Comparison of fracture resistance and failure pattern of endodontically treated premolars with different esthetic onlay systems: An in vitro study

AIM: To compare the fracture resistance and modes of failures of three different aesthetic MOD onlays on endodontically treated premolars. MATERIALS AND METHODS: Forty sound maxillary premolars were selected of which 10 untreated teeth were taken as control (Group I). The other thirty premolars were subjected to standardized MOD onlay preparations and root canal treatments and divided into 3 equal groups. Onlays were prepared in Group II- Indirect composite, Group III- Lithium Disilicate ceramic and Group IV- Full Zirconia. All onlays were cemented using Multilink Automix. All the 40 samples were subjected to fracture resistance testing on Universal testing machine. Also fractured specimens were observed under stereo-microscope for modes of failure. RESULTS: Group IV presented the highest fracture resistance. Groups II and III presented no significant difference in fracture resistance from each other (P > 0.05). Group II and Group III showed significantly lower fracture resistance values than Group I. Coming to modes of failure, only Group IV had showed no cracks in any of the restorations. CONCLUSION: Full Zirconia MOD onlays increased the fracture resistance of endodontically treated premolars to a significantly higher level than the sound teeth.